Internal heat exchanger for automotive air conditioner

ABSTRACT

An internal heat exchanger for an automotive air conditioner which is capable of securing length of the internal heat exchanger necessary for heat exchange by a double pipe even when an evaporator and an expansion valve are disposed where the distance to a partition wall is short. Between an expansion valve and evaporator, and a partition wall, a first double pipe is disposed which is formed by surrounding an inner pipe connected to an inlet port of the expansion valve with an outer pipe connected to an outlet port of the evaporator, and a second double pipe is disposed within an engine room which is formed by surrounding an inner pipe with an outer pipe, in a manner extended from the first double pipe. The first double pipe and the second double pipe are connected by a pipe connecting member such that the connecting portions of the pipes are prevented from disconnection.

CROSS-REFERENCES TO RELATED APPLICATION

This application claims priority of Japanese Application No. 2007-044500filed on Feb. 23, 2007 and entitled “Internal Heat Exchanger forAutomotive Air Conditioner”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an internal heat exchanger for an automotiveair conditioner, and more particularly to an internal heat exchanger foran automotive air conditioner, for performing heat exchange betweenhigh-temperature refrigerant having flowed out from a condenser andlow-temperature refrigerant returning to a compressor, within arefrigeration cycle of an automotive air conditioner.

2. Description of the Related Art

For automotive air conditioners, it has been proposed in view ofenvironmental problems that refrigerant used in refrigeration cyclesthereof should be switched from a substitute flon (HFC-134a) to naturalrefrigerant (carbon dioxide). Although the system of a refrigerationcycle using carbon dioxide as refrigerant has the same basic structure,in general, to enhance the efficiency of the system, an internal heatexchanger is used in the refrigeration cycle using carbon dioxide (seee.g. Japanese Unexamined Patent Application Publication No.2001-108308).

The internal heat exchanger is configured such that heat exchange isperformed between refrigerant flowing through a passage from a gascooler that cools high-temperature, high-pressure refrigerant compressedby a compressor to an expansion valve and refrigerant flowing through apassage from an accumulator to the compressor. This causes refrigeranthaving flowed out from the gas cooler to be further cooled by theinternal heat exchanger whereby the enthalpy of refrigerant lowered atthe inlet ports of the expansion valve and an evaporator. Further,refrigerant drawn from the accumulator is further superheated by theinternal heat exchanger whereby the enthalpy of the refrigerant isincreased at the inlet of the compressor, so that it is possible toenhance the efficiency of the system, that is, the performancecoefficient and cooling power of the refrigeration cycle.

In contrast, also for a refrigeration cycle using HFC-134a or gaseshaving characteristics equivalent or similar to HFC-134a, asrefrigerant, a system employing the internal heat exchanger iscontemplated, and it is expected that the efficiency of the system isimproved.

The internal heat exchanger as described above has a high-pressurepassage and a low-pressure passage formed therein, for passinghigh-temperature, high-pressure refrigerant, and for passinglow-temperature, low-pressure refrigerant, respectively, and isconfigured such that heat can be exchanged between refrigerants flowingthrough these passages. The high-pressure passage has a pipe connectedto an inlet side thereof for receiving condensed liquid refrigerant sentfrom a receiver, and a pipe connected to an outlet side thereof fordelivering the liquid refrigerant to the expansion valve. Thelow-pressure passage has a pipe connected to an inlet side thereof, forreceiving refrigerant having flowed from the evaporator, and a pipeconnected to an outlet side thereof for delivering the refrigerant tothe inlet of the compressor.

In contrast, the present applicant has proposed to cause pipes of therefrigeration cycle to function as an internal heat exchanger instead ofdisposing an independent device of the internal heat exchanger in therefrigeration cycle (Japanese Patent Application No. 2006-338152).According to this proposal, a double pipe, which is formed byconcentrically arranging a high-pressure pipe for passinghigh-temperature, high-pressure refrigerant, and a low-pressure pipe forpassing low-temperature, low-pressure refrigerant, is disposed such thatheat exchange is performed between refrigerant flowing through an innerpipe, and refrigerant flowing through a space between the inner pipe andan outer pipe, via the inner pipe. At one end of the double pipe, thehigh-pressure pipe is connected to an inlet of the expansion valve whichhas the evaporator disposed adjacent thereto, and the low-pressure pipeis connected to an outlet of the evaporator. Further, to the other endof the double pipe is attached a pipe joint for branching the passagesof the double pipe. The pipe joint is disposed such that an end facethereof which has two independent openings for the branches is exposedto the engine room at a partition wall which separates the engine roomand a vehicle compartment, whereby the high-pressure pipe from thereceiver and the low-pressure pipe to the compressor both disposed inthe engine room are separately attached to the end face of the pipejoint. This is because as to the procedure of assembly in the engineroom, a pipe of a high-pressure system can be disposed in advance, but apipe of a low-pressure system is required to be attached to thecompressor after the engine is finally mounted in the engine room, sincethe compressor is mounted on the engine, and hence it is necessary toconnect the pipe of the low-pressure system and the pipe of thehigh-pressure system in the engine room separately from connection ofthe evaporator and the expansion valve in the vehicle compartment. Morespecifically, in the above-described proposal, the evaporator and theexpansion valve within the vehicle compartment are connected to thepartition wall by the double pipe so as to cause the double pipe aspiping in the vehicle compartment to serve as the internal heatexchanger.

As described above, the construction for causing the double pipe aspiping laid between the evaporator and the expansion valve, and thepartition wall to serve as the internal heat exchanger does notnecessarily function effectively since the disposed locations of theevaporator and the expansion valve in the vehicle compartment aredifferent depending on the vehicle. For example, when the evaporator andthe expansion valve are arranged in the vicinity of the partition wall,the double pipe laid between the evaporator and the expansion valve, andthe partition wall inevitably becomes short. This causes a problem inthat the double pipe cannot secure a sufficient length necessary forperforming heat exchange.

SUMMARY OF THE INVENTION

The present invention has been made in view of these points, and anobject thereof is to provide an internal heat exchanger for anautomotive air conditioner which is capable of securing a sufficientlength of the internal heat exchanger necessary for heat exchange evenwhen a double pipe disposed between a partition wall, and an evaporatorand an expansion valve is short.

To attain the above object, there is provided an internal heat exchangerfor an automotive air conditioner, for performing heat exchange betweenhigh-temperature, high-pressure refrigerant condensed within arefrigeration cycle, and low-temperature, low-pressure refrigerantevaporated within the refrigeration cycle, comprising a first doublepipe that is disposed between an inlet port of an expansion valve and anoutlet port of an evaporator, arranged in a compartment of a vehicle,and a partition wall for separating an engine room of the vehicle andthe compartment of the vehicle, such that a first outer pipe is disposedin a manner surrounding a first inner pipe, a second double pipe that isdisposed within the engine room, such that a second outer pipe isdisposed in a manner surrounding a second inner pipe, the second innerpipe and the second outer pipe being connected to the first inner pipeand the first outer pipe at the partition wall, and a pipe-connectingmember that connects the first double pipe and the second double pipesuch that connecting portions thereof are prevented from beingdisconnected from each other.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings which illustrate preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an example of mounting of an internal heatexchanger according to a first embodiment of the present invention andan expansion valve.

FIGS. 2A and 2B are views of an internal heat exchanger according to asecond embodiment of the present invention, in which FIG. 2A is across-sectional view of part of a first double pipe, and FIG. 2B is across-sectional view of part of a second double pipe.

FIG. 3 is a cross-sectional view of an internal heat exchanger accordingto a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will now be described in detail with reference to drawingsshowing a preferred embodiment thereof.

FIG. 1 is a view showing an example of mounting of an internal heatexchanger according to a first embodiment of the present invention andan expansion valve.

In a refrigeration cycle of an automotive air conditioner, a compressor,a condenser, and a receiver, none of which are shown, are arranged in anengine room of a vehicle, and an expansion valve 2 and an evaporator 3are arranged in a vehicle compartment separated from the engine room bya partition wall 1. In the illustrated example, the expansion valve 2 isaccommodated in a casing 4 which is mounted on an end face of theevaporator 3 in a manner covering an inlet port and an outlet port ofthe evaporator 3. Within the casing 4, a refrigerant outlet of theexpansion valve 2 is connected to the inlet port of the evaporator 3.The expansion valve 2 and the evaporator 3 within the vehiclecompartment are connected to the receiver and the compressor within theengine room via the internal heat exchanger 10.

The internal heat exchanger 10 is separated into a first double pipe 11on the vehicle compartment side and a second double pipe 12 on theengine room side with the partition wall 1 as a boundary. The firstdouble pipe 11 comprises an inner pipe 11 a and an outer pipe 11 bdisposed concentrically with the inner pipe 11 a in a manner surroundingthe same. Similarly, the second double pipe 12 comprises an inner pipe12 a and an outer pipe 12 b disposed concentrically with the inner pipe12 a in a manner sounding the same.

The inner pipe 11 a of the first double pipe 11 extends into the casing4 through an opening formed in a side surface of the casing 4, and isdirectly connected to the inlet port of the expansion valve 2accommodated in the casing 4 such that the inner pipe 11 a supplieshigh-temperature, high-pressure refrigerant to the expansion valve 2.The outer pipe 11 b is connected to the opening formed in the sidesurface of the casing 4 such that low-temperature, low-pressurerefrigerant derived from the evaporator 3 is guided into a space betweenthe outer pipe 11 b and the inner pipe 11 via the casing 4.

The first double pipe 11 is flexibly formed, and hence to reinforce anend thereof opposite to an end thereof attached to the casing 4, ahollow cylindrical reinforcing member 14 is joined to the outer pipe 11b, and a shock-absorbing support material 13 is mounted on an outerperiphery of the reinforcing member 14. The shock-absorbing supportmaterial 13 is pressed against the partition wall 1 by the elasticity ofthe first double pipe 11, and in this state, supports the reinforcingmember 14 disposed to extend through a through hole 1 a of the partitionwall 1.

On the other hand, the second double pipe 12 has the inner pipe 12 athereof connected to the inner pipe 11 a of the first double pipe 11,and the outer pipe 12 b thereof connected to the reinforcing member 14.A pipe-connecting member 15 is fitted on respective connecting portionsof the reinforcing member 14 and the outer pipe 12 b, and constrainsrespective ribs formed on the reinforcing member 14 and the outer pipe12 b to each other to thereby hold the reinforcing member 14 and theouter pipe 12 b connected in a state prevented from being disconnectedfrom each other. Further, in the illustrated example, a joint member 16bent into an L-shape is joined to an end of the outer pipe 12 b oppositeto the connecting portion thereof. After an engine is placed in theengine room, an intake pipe of the compressor mounted on the engine isconnected to the joint member 16. Further, in the illustrated example,the inner pipe 12 a of the second double pipe 12 is extended out throughthe joint member 16, and a portion of the joint member 16 from which theinner pipe 12 a extends out is hermetically joined to the inner pipe 12a by brazing. A part of the inner pipe 12 a extended out of the jointmember 16 serves as a pipe for introducing high-temperature,high-pressure refrigerant.

Next, a description will be given of the operation of the refrigerationcycle including the internal heat exchanger configured as above. Itshould be noted that arrows appearing in FIG. 1 indicate respectivedirections of refrigerant flow.

First, although not shown in FIG. 1, within the engine room, thecompressor is driven by the engine to compress refrigerant, and thecompressed high-temperature, high-pressure refrigerant is condensed bythe condenser. The condensed refrigerant is separated into gas andliquid by the receiver, and the liquid refrigerant obtained by thegas/liquid separation is introduced into the internal heat exchanger 10.The liquid refrigerant introduced into the internal heat exchanger 10flows through the inner pipe 12 a of the second double pipe 12 and theinner pipe 11 a of the first double pipe 11, and is sent to theexpansion valve 2. The expansion valve 2 throttles and expands theliquid refrigerant into low-temperature, low-pressure refrigerant, andsupplies the low-temperature, low-pressure refrigerant into theevaporator 3. In the evaporator 3, the supplied refrigerant exchangesheat with air in the vehicle compartment whereby it is evaporated, whichcools the air in the vehicle compartment. The refrigerant evaporated bythe evaporator 3 is introduced into the internal heat exchanger 10through the casing 4. The refrigerant introduced into the internal heatexchanger 10 is caused to flow through a passage between the inner pipe11 a and the outer pipe 11 b of the first double pipe 11 and a passagebetween the inner pipe 12 a and outer pipe 12 b of the second doublepipe 12, and then flows through the joint member 16 to the intake pipe,to be drawn into the compressor.

The expansion valve 2 controls the flow rate of refrigerant sent intothe evaporator 3 based on the temperature and pressure of refrigeranthaving flowed out from the evaporator 3, whereby refrigerant passingthrough the evaporator 3 is completely evaporated, and further therefrigerant having flowed out from the evaporator 3 is controlled suchthat it has a predetermined degree of superheat.

Further, the internal heat exchanger 10 performs heat exchange betweenthe high-temperature, high-pressure refrigerant flowing through theinner pipe 12 a of the second double pipe 12 and the inner pipe 11 a ofthe first double pipe 11, and the low-temperature, low-pressurerefrigerant flowing through the passage between the inner pipe 11 a andouter pipe 11 b of the first double pipe 11 and the passage between theinner pipe 12 a and outer pipe 12 b of the second double pipe 12. Thiscauses refrigerant entering the expansion valve 2 to be further cooledby the internal heat exchanger 10 whereby the enthalpy of refrigerant atthe inlet port of the expansion valve 2 and further that of refrigerantat the inlet port of the evaporator 3 are reduced, and at the same timecauses refrigerant drawn into the compressor to be further superheatedby the internal heat exchanger 10 whereby the enthalpy of refrigerant atan inlet port of the compressor is increased. This makes it possible toenhance the performance coefficient of the refrigeration cycle, which isrepresented by the ratio with the enthalpy difference between the inletport of the evaporator 3 and the inlet port of the compressor and theenthalpy difference between the inlet port and an outlet port of thecompressor, thereby making it possible to improve the cooling power ofthe refrigeration cycle and the efficiency of the system.

As described above, the internal heat exchanger 10 is configured to beconnectably separated at an intermediate portion, so that also in avehicle in which the distance from the expansion valve 2 and theevaporator 3 to the through hole 1 a of the partition wall 1 is short,the internal heat exchanger 10 can be extended into the engine room bythe second double pipe 12, whereby it is possible to ensure a lengthsufficient for heat exchange, which cannot be ensured only by the firstdouble pipe 11.

Further, the internal heat exchanger 10 is configured such thathigh-pressure refrigerant is caused to flow through the inner pipe 11 aof the first double pipe 11 and the inner pipe 12 a of the second doublepipe 12, and hence even if refrigerant leaks via connecting portions ofthe inner pipes, it leaks into the low-pressure side passages, whicheliminates the fear that refrigerant leaks into the atmosphere.

FIGS. 2A and 2B are views of an internal heat exchanger according to asecond embodiment of the invention. FIG. 2A is a cross-sectional view ofpart of a first double pipe, and FIG. 2B is a cross-sectional view ofpart of a second double pipe. It should be noted that in FIGS. 2A and2B, component elements identical to those shown in FIG. 1 are designatedby identical reference numerals, and detailed description thereof isomitted.

As is distinct from the internal heat exchanger according to the firstembodiment in which low-pressure refrigerant returning from theevaporator 3 to the compressor is caused to flow though the passagesbetween the respective inner pipes and the outer pipes associatedtherewith, in the internal heat exchanger according to the secondembodiment, high-pressure refrigerant is caused to flow though thepassages.

The constructions of the expansion valve 2 and the casing 4 to which isconnected the first double pipe 11 are the same as those shown in FIG.1, and the inlet port of the expansion valve 2 is positionedsubstantially in the center of the opening formed in the side surface ofthe casing 4, and therefore in the present internal heat exchanger, theconstruction of the first double pipe 11 to which are connected theexpansion valve 2 and the casing 4 is changed. More specifically, asshown in FIG. 2A, in the first double pipe 11, a connecting member 17for changing the direction of refrigerant flow is joined to an end(upper end as viewed in FIG. 2A) of the first double pipe 11 to whichare connected the expansion valve 2 and the casing 4. The connectingmember 17 has a hollow cylindrical portion 17 a formed substantially inthe center thereof such that the hollow cylindrical portion 17 a extendstoward the casing 4. The central opening of the hollow cylindricalportion 17 a is formed such that it extends approximately to the centerof the connecting member 17 in the direction of the depth thereof towardthe first double pipe 11, and further extends therefrom through a sideof the hollow cylindrical portion 17 a. Thus, the hollow cylindricalportion 17 a forms a high-pressure passage of the internal heatexchanger, and is connected to the inlet port of the expansion valve 2.Further, the connecting member 17 has a low-pressure passage 17 b inwhich part of the periphery of the hollow cylindrical portion 17 aextends therethrough to an end face (lower end face, as viewed in FIG.2A) thereof opposite from an end thereof connected to the inlet port ofthe expansion valve 2 such that the part is generally U-shaped incross-section. The lower end face of the connecting member 17 is formedto have a hollow cylindrical shape, and is joined to the inner pipe 11 aof the first double pipe 11. Furthermore, the connecting member 17 isjoined to the outer pipe 11 b of the first double pipe 11 at a positionupstream of the position where the high-pressure passage is open. Thismakes it possible to interchange the refrigerant flows between theinside and outside the inner pipe 11 a of the first double pipe 11 witheach other.

On the other hand, the second double pipe 12 has the inner pipe 12 aexpanded on a side thereof opposite to the side where it is connectedthe first double pipe 11, whereby the inner pipe 12 a and the outer pipe12 b are joined to each other at their contact portions to close thepassage formed between the inner pipe 12 a and the outer pipe 12 b. Theouter pipe 12 b is joined to a high-pressure pipe 5 for introducinghigh-temperature, high-pressure refrigerant, in the vicinity of whereouter pipe 12 b and the inner pipe 12 are joined. Further, the expandedportion of the inner pipe 12 a forms a joint for connecting the seconddouble pipe 12 to the intake pipe of the compressor.

The first double pipe 11 and the second double pipe 12 are connected atthe partition wall 1 by a generally employed method for connectingbetween double pipes.

The internal heat exchanger according to the second embodiment isconfigured such that high-temperature, high-pressure refrigerant iscaused to flow through the passage between the inner pipe 11 a and outerpipe 11 b of the first double pipe 11, and the passage between the innerpipe 12 a and outer pipe 12 b of the second double pipe 12, so that theouter pipe 11 b of the first double pipe 11 and the outer pipe 12 b ofthe second double pipe 12 always have a high temperature. This preventsdew condensation on the internal heat exchanger, thereby making itunnecessary to cover the outer periphery of the internal heat exchangerwith a heat insulator.

FIG. 3 is a cross-sectional view of an internal heat exchanger accordingto a third embodiment of the present invention. It should be noted thatin FIG. 3, component elements identical to those shown in FIG. 1 andFIGS. 2A and 2B are designated by identical reference numerals, anddetailed description thereof is omitted.

The internal heat exchanger according to the third embodimentinterchanges the directions of refrigerant flows in the vehiclecompartment and the engine room with each other. The first double pipe11 in the vehicle compartment is configured such that high-temperature,high-pressure refrigerant is caused to flow through the passage betweenthe inner pipe 11 a and outer pipe 11 b, and low-temperature,low-pressure refrigerant is caused to flow through the inner pipe 11 a.The second double pipe 12 in the engine room is configured such thathigh-temperature, high-pressure refrigerant is caused to flow throughthe inner pipe 12 a, and low-temperature, low-pressure pressurerefrigerant is caused to flow through the passage between the inner pipe12 a and outer pipe 12 b.

To this end, the first double pipe 11 has opposite ends thereof providedwith connecting members 17 and 18 for changing the direction of arefrigerant flow. The connecting member 17 connected to the expansionvalve 2 and the casing 4 is the same as the connecting member 17provided in the internal heat exchanger according to the secondembodiment, and a high-pressure pipe 19 connected to the opening of theinlet port of the expansion valve 2 is joined to the hollow cylindricalportion 17 a extending axially outward from approximately the center ofthe connecting member 17. The connecting member 18 is connected to thesecond double pipe 12 in the engine room, and a high-pressure pipe 20,to which is connected the inner pipe 12 a of the second double pipe 12,is joined to a hollow cylindrical portion 18 a extending axially outwardfrom approximately the center of the connecting member 18. The outerpipe 12 b of the second double pipe 12 is inserted into an outer hollowcylindrical portion 18 b of the connecting member 18. The outer hollowcylindrical portion 18 b is formed into a shape in which the cylindricalportion 18 b and the outer pipe 12 b are connected to each other by thepipe-connecting member 15.

The second double pipe 12 is the same as the second double pipe 12disposed in the internal heat exchanger 10 according to the firstembodiment. To an end of the outer pipe 12 b is joined the L-shapedjoint member 16, and the inner pipe 12 a is extended out through thejoint member 16. To an end of the inner pipe 12 a is joined thehigh-pressure pipe 5 disposed between the internal heat exchanger 10 andthe receiver.

Although in the first to third preferred embodiments described above,the descriptions have been given of the example of the construction inwhich low-pressure or high-pressure refrigerant is caused to flowthrough the outer pipe 11 b of the first double pipe 11 and the outerpipe 12 b of the second double pipe 12, and the example of theconstruction in which high-pressure refrigerant is caused to flowthrough the outer pipe 11 b of the first double pipe 11 and low-pressurerefrigerant is caused to flow through the outer pipe 12 b of the seconddouble pipe 12, the internal heat exchanger 10 may be configured suchthat low-pressure refrigerant is caused to flow through the outer pipe11 b of the first double pipe 11 and high-pressure refrigerant is causedto flow through the outer pipe 12 b of the second double pipe 12.

The internal heat exchanger of the automotive air conditioner accordingto the present invention is capable of separately arranging the firstdouble pipe and the second double pipe in the vehicle compartment andthe engine room, and hence it is possible to allocate the length of theinternal heat exchanger necessary for heat exchange, also to the engineroom side in a vehicle in which the evaporator and the expansion valveare arranged in the vicinity of the partition wall. Further, part of theinternal heat exchanger is disposed in a manner extended into the engineroom, whereby an end of the internal heat exchanger on a side connectedto the intake pipe of the compressor is positioned forward of thepartition wall, which is difficult to access during work. This makes iteasy to connect between the compressor secured on the engine and theintake pipe of the compressor, after the engine has been mounted in theengine room.

The foregoing is considered as illustrative only of the principles ofthe present invention. Further, since numerous modifications and changeswill readily occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and applications shown anddescribed, and accordingly, all suitable modifications and equivalentsmay be regarded as falling within the scope of the invention in theappended claims and their equivalents.

1. An internal heat exchanger for an automotive air conditioner, forperforming heat exchange between high-temperature, high-pressurerefrigerant condensed within a refrigeration cycle, and low-temperature,low-pressure refrigerant evaporated within the refrigeration cycle,comprising: a first double pipe that is disposed between an inlet portof an expansion valve and an outlet port of an evaporator, arranged in acompartment of a vehicle, and a partition wall for separating an engineroom of the vehicle and the compartment of the vehicle, such that afirst outer pipe is disposed in a manner surrounding a first inner pipe;a second double pipe that is disposed within the engine room, such thata second outer pipe is disposed in a manner surrounding a second innerpipe, said second inner pipe and said second outer pipe being connectedto said first inner pipe and said first outer pipe at the partitionwall; and a pipe-connecting member that connects said first double pipeand said second double pipe such that connecting portions thereof areprevented from being disconnected from each other.
 2. The internal heatexchanger as claimed in claim 1, wherein said second double pipe hassaid second outer pipe joined to a joint member for connection to anintake pipe of a compressor, said second inner pipe being extended outthrough said joint member.
 3. The internal heat exchanger as claimed inclaim 2, wherein said second inner pipe is integrally formed with a pipefor introducing high-temperature, high-pressure refrigerant.
 4. Theinternal heat exchanger as claimed in claim 1, wherein said first doublepipe includes a connecting member being joined to said first inner pipeand said first outer pipe at an end of said connecting member oppositeto a side where said first double pipe is connected to said seconddouble pipe, whereby said connecting member has a hollow cylindricalbody of a high-pressure passage formed to extend axially in anapproximately central position of said first inner pipe such that acentral opening of said hollow cylindrical body communicates with aspace formed between said first inner pipe and said first outer pipe,and a low-pressure passage formed therethrough to an end face on a sidewhere part of a periphery of said hollow cylindrical body is joined tosaid first inner pipe, and wherein said second double pipe closes apassage formed between said second inner pipe and said second outer pipeon a side opposite from a side where said first double pipe is connectedto said second double pipe, and has a pipe joined thereto forintroducing high-temperature, high-pressure refrigerant into thepassage, said second inner pipe extended outward of a joint position ofsaid second outer pipe and said pipe, to form a joint for beingconnected to an intake pipe of a compressor.
 5. An internal heatexchanger as claimed in claim 1, wherein said first double pipe hasconnecting members at respective opposite ends thereof, each connectingmember having a hollow cylindrical body of a high-pressure passageformed to extend axially in an approximately central position of saidfirst inner pipe such that a central opening of said hollow cylindricalbody communicates with a space formed between said first inner pipe andsaid first outer pipe, and a low-pressure passage formed therethrough toan end face on a side where part of a periphery of said hollowcylindrical body is joined to said first inner pipe